Effects of rearing conditions on aging characteristics and pathobiological phenotypes in SAMP10 mice

Abstract

The purpose of this study was to obtain background data regarding aging characteristics and pathobiological phenotypes in SAMP10/Ta (P10) and SAMR1TA (R1) mice reared under specific pathogen-free (SPF) conditions and compare the data with those of P10 and R1 mice reared under conventional conditions at Kyoto University. Senescence scores were suppressed, and life span was prolonged in both strains under SPF conditions. However, there was still a significant difference between P10 and R1 in both life span and senescence scores under SPF conditions, suggesting a well preserved “accelerated senescence” in P10 mice even under SPF conditions. In P10 mice that died naturally, the incidence of amyloidosis, abscess and contracted kidney was reduced significantly under SPF conditions. However, the incidence of lymphoid cell neoplasms and pulmonary congestion and edema was increased significantly under SPF conditions. In P10 mice, loss of brain weight manifested somewhat later under SPF conditions. Morphometrically, age-related involutional changes were evident mainly in the frontal portion of the cerebrum. The tail suspension test revealed an age-related increase in immobility times. Thus, P10-specific pathologies, brain atrophy and emotional disorder were also preserved even under SPF conditions. In R1 mice, these phenotypes were not observed under either set of conditions.